A 58 year, female with history of SLE under medication presented to the emergency department with complaints of excruciating knee pain radiating to thigh. She reported similar pain about a week back for which she attended the emergency department and was given pain medications, after which the pain subsided. No history of trauma was given. The patient was referred for emergency ultrasound to rule out DVT or ruptured baker’s cyst. X-ray pelvis was done to rule out avascular femoral necrosis.
X-ray pelvis was within normal limits. Ultrasound of right knee was negative for baker’s cyst or DVT with small amount of suprapatellar knee joint effusion and medial extrusion of the body of medial meniscus. Since the severity of pain was out of proportion to the imaging findings, MRI was advised.
MRI with contrast showed a long segment of diffuse marrow disease appearing T1 hypointense, T2/STIR hyperintense with heterogeneous contrast enhancement involving the proximal & mid shaft of femur with surrounding enhancing periosteal edema and nodular extra-osseous soft tissue component exhibiting restricted diffusion. Small focal areas of endosteal erosion in the posterior cortex of proximal femoral shaft. However, no frank cortical breach was seen. A small similar area of marrow signal abnormality was noted in the right intertrochanteric region.
PET CT was done which showed multifocal areas of increased uptake involving the bilateral femurs, angle of right mandible, left glenoid, left 9th rib, L2, L4 and L5 vertebral bodies, left pubis & left iliac bone. No significant regional lymph nodal disease noted.
A USG guided biopsy was performed of the soft tissue component adjacent to the right femur. Histopathological diagnosis of diffuse large B cell lymphoma (DLBCL) was given.
Background
Lymphoma represents a relatively well-recognized malignant phenomenon associated with lupus.[1]. Primary bone lymphoma is a rare extranodal presentation of non-Hodgkin’s lymphoma. Primary bone diffuse large B-cell lymphoma (DLBCL) is the most common pathological type, comprising about 80% of PBL.[2]A study examining predictors of increased lymphoma risk in systemic lupus suggested a potential role of cyclophosphamide and high cumulative steroid use. [3]
Clinical Perspective
Fever, adenopathy, weight loss are shared clinical features in SLE-related lymphoma and infections complicating SLE. Bone pain & swelling are the most common presenting symptoms of PBL. However, these features are not typical of lymphoma and can be associated with other marrow infiltrative etiologies. Therefore, a thorough assessment of the duration and chronicity of symptoms, exhaustive exclusion of other potential etiologies, and examination of tissue and bone marrow biopsies are essential in arriving at the right diagnosis. [4, 5]
Imaging Perspective
MR imaging feature that is suggestive of infiltrative processes such as PBL is the replacement of bone marrow, especially in the setting of near-normal radiographic findings. Another and even more specific feature of round cell tumours such as lymphoma is the relatively minimal cortical destruction in the presence of extensive soft tissue and marrow involvement. Observation of these two factors in patients with suspected bone lymphoma will add a further degree of certainty to the diagnosis. FDG-PET exhibits increased uptake and demonstrates other areas of involvement. CT scan is helpful in evaluating erosion and biopsy guidance. Lastly, the consideration of lymphoma in the appropriate differential diagnosis is important to ensure that an adequate biopsy sample be obtained for immunophenotyping and other analysis. [6]
Take-Home Message / Teaching Points
Primary bone lymphoma should always be considered as a differential diagnosis in patients exhibiting diffuse marrow changes with soft tissue component and relatively little cortical destruction. MR imaging in conjunction with PET/CT and biopsy is helpful in suggesting the diagnosis leading to early treatment.
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Metastatic primary bone diffuse large B-cell lymphoma in a known case of SLE
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1. MRI: Extensive abnormal signals are observed in the femoral shaft and adjacent bone marrow areas, indicating significant bone marrow infiltration. On T1WI, the signals appear nearly isointense or hypointense, and on T2WI, they appear relatively hyperintense or mixed. A localized soft tissue mass is visible, accompanied by relatively mild cortical bone destruction.
2. CT: Irregular areas of decreased density are noted on both sides of the femoral shaft, suggesting infiltration of abnormal tissue into the bone marrow cavity; on the soft tissue window, a mass-like lesion is seen, with some cortical bone destruction, though limited in extent.
3. PET-CT: A focus of high metabolic abnormal uptake is seen in the femoral region, indicating a highly active lesion. Meanwhile, abnormal uptake is also found in other skeletal sites and lymph nodes, presenting an imaging pattern of multifocal lesions consistent with lymphoma.
4. Ultrasound (Thigh Soft Tissue Scan): An abnormal hypoechoic or mixed echogenic region is detected in the posterior thigh soft tissues, with relatively indistinct boundaries and potentially increased blood flow signals, suggesting soft tissue infiltration or a neoplastic lesion.
Considering the patient’s age, history of SLE, background of immunosuppressive therapy, and imaging characteristics (especially diffuse marrow infiltration, significant soft tissue components, relatively mild cortical destruction, and high metabolic lesions on PET-CT), and referencing literature reports, these findings are most consistent with Primary Bone Lymphoma. Pathological examination (histology and immunophenotyping) confirming diffuse large B-cell lymphoma (DLBCL) or another lymphoma type would provide a definitive diagnosis.
(1) Chemotherapy and Radiotherapy: For Primary Bone Lymphoma, chemotherapy (e.g., R-CHOP regimen) is typically the mainstay of treatment. Local lesions may also be managed with radiotherapy to consolidate the therapeutic effect.
(2) Immunomodulation and Supportive Care: Given the patient’s underlying SLE, a careful balance between immunosuppression and antitumor therapy is necessary. Close collaboration with rheumatology and hematology is advised to re-evaluate and adjust lupus management. Attention to bone marrow suppression risks is crucial, along with prophylactic anti-infection measures and correction of anemia and thrombocytopenia.
(3) Surgical Intervention: Surgery is generally reserved for cases with significant bone destruction and risk of pathological fracture or for obtaining an adequate biopsy sample. Since lymphoma is typically responsive to chemotherapy and radiotherapy, extensive surgery is not a primary option.
Considering the patient’s bone involvement, potential fracture risk, and a compromised immune status due to SLE, exercise should be cautious and individualized in accordance with the FITT-VP principle:
Key points during rehabilitation include:
This report is based solely on the provided medical history and imaging data. It is intended as an academic reference for clinical diagnosis and therapeutic decision-making and does not substitute for in-person evaluation or professional medical advice. Specific treatment and rehabilitation plans should be implemented in conjunction with complete clinical data and the attending physician’s comprehensive assessment.
Metastatic primary bone diffuse large B-cell lymphoma in a known case of SLE
